The following is a list of some prior art related to the present invention:
U.S. Pat. No. 4,379,252, April 1983, D. E. Work and S. G. Johnson
U.S. Pat. No. 4,527,086, July 1985, J. Maya.
The present invention relates in general to a mercury-containing arc discharge device for converting electrical energy into resonance radiation. More particularly, the present invention is concerned with an improved isotopic mixture of mercury for providing improved efficiency of the device. An example of such a device is a fluorescent lamp.
The basis for the common tubular fluorescent lamp is an electrical discharge in a mixture of mercury vapor and the rare gas argon. Energetic electrons excite the mercury atoms which emit ultraviolet light, which passes to a phosphorescent material coating the inside of the glass tube, and the light is re-emitted as light in the visible spectrum. In passing to the coating the ultraviolet light is absorbed and re-emitted many times by the mercury atoms. In the process some of the excited mercury atoms may lose their energy in ‘quenching’ collisions with electrons and argon atoms. About 20 percent of the energy of exciting the mercury is lost in way.
About 1978 physicists at the GTE Sylvania Laboratories discovered that adding the isotope mercury-199 to the naturally occurring mixture of mercury isotopes could improve the efficiency of fluorescent lamps by providing an alternative route for the ultraviolet light to reach the tube wall. Tests showed that efficiency could be improved by as much as 5 percent with addition of 2 to 4 percent mercury-196 to natural mercury. The improved device was patented by D. E. Work and S. G. Johnson (U.S. Pat. No. 4,379,252, April 1983), reported by J. Maya et al. in the journal Science (Vol. 226, p. 435, 1984), and described in Science News (Vol. 126, p. 262, 1984). Another version, with an altered composition of mercury isotopes, was patented by J. Maya a year later (U.S. Pat. No. 4,527,086, July 1985).
In the United States fluorescent lamps consume about 2.5 percent of the electrical power produced or 250 billion kilowatt-hours per year. At 10 cents per kilowatt-hour that adds up to 25 billion dollars per year. Saving 5 percent is worth about 1.25 billion dollars per year. Saving 1 percent is worth about 250 million dollars per year. For a 40-watt lamp with a lifetime of 4000 hours this corresponds to 80 cents per lamp over its lifetime.
The use of a tailored mercury isotope mixture would require essentially no changes in lamp manufacture and no changes whatsoever in lamp fixtures. Compact fluorescent lamps operate in the same way as the standard tubular lamps. Their performance is expected to be similarly improved with use of mercury-196.
In the late 1980's GTE Sylvania decided not to manufacture lamps with the mercury-196 added to improve performance. One must guess that it was determined that a somewhat higher price of lamps having a modified mercury composition would limit sales and that the venture was abandoned for that reason.
In 2011 the situation is quite different. Improving lamps by adding mercury-196 is more important and less costly because:                1) Global warming is an environmental consideration.        2) Oil imports from the Middle East are a political and economic consideration.        3) Compact fluorescent lamps are replacing incandescent lamps.        4) Mercury in used fluorescent lamps is (or can be) collected and recycled.        5) With better phosphors now available less mercury is required in each lamp.        6) New energy efficiency requirements imposed by the European Union (as of September 2009) and in the United States (starting in January 2011) favor fluorescent lamps over traditional incandescent lamps.        
Standard mercury-rare gas fluorescent lamps have an output of 85 lumens per watt of input power, and are far more efficient than tungsten-filament lamps with only 15 lumens per watt. Currently available LED (light emitting diode) lamps producing white light yield about 30 lumens per watt. Laboratory models are reported to be several times more efficient. It seems likely the LEDs will be improved further, but low-cost fluorescent lamps may be expected to dominate the lighting market for many years.
Clearly, a higher efficiency fluorescent lamp is a useful device. Altering the isotopic composition of the mercury in such lamps as described in the patents mentioned above (U.S. Pat. Nos. 4,379,252 and 4,527,086) can increase the efficiency.
In 1983-1985 I developed a Monte Carlo method for the theoretical treatment of the emission, transmission, and absorption of resonance radiation which was successful in predicting experimental measurements of the ultraviolet spectra and the improvements in efficiency of the lamps with increased mercury-196. This was reported in the journal Physical Review A (J. B. Anderson et al., Vol. 31, p. 2968 (1985). This calculation method has been used quite successfully by a number of scientists in the past 25 years for predicting and understanding the performance of fluorescent lamps and related devices.
I recently reviewed my earlier Monte Carlo calculations in an effort to determine whether they might be applicable to the newer compact fluorescent lamps. I found that the earlier results and conclusions were readily transferred to the compact lamps.
This review led to an important patentable discovery: I discovered new and novel isotopic compositions of mercury that provide improvements in efficiency of fluorescent lamps with less expensive mercury mixtures than those known before. These mixtures yield higher efficiencies than others having similar amounts of the expensive isotope mercury-196.